1. Field of the invention
The invention relates to a gas turbine engine which is provided with a braking device for ensuring full control of the rotational speed of the turbine in the event of breakage of the connecting shaft between the turbine and the compressor.
2. Discussion of the prior art
French Patents Nos. 2 052 055 and 2 181 529 relate to the problems raised by the onset of autorotation of a turbojet rotor in the event of a breakdown of the turbojet engine, and propose a solution which achieves immobilization of the rotor without mechanical braking. Instead, the solution makes use of a jet deflection or reverse device associated with the turbojet engine to stop the flow of air which drives the rotor.
A closely related problem is posed by the accidental breakage of a connecting shaft between a compressor and turbine of a turboshaft engine. Indeed, if suitable measures are not taken, this results in the turbine rotor rotating at excessive speeds, with the associated risk of shattering of the rotor leading to damage to the adjoining structures and often catastrophic consequences. French Patent No. 2 131 797 proposes a solution to this problem which involves special mounting arrangements for a rotary unit of the turboshaft engine comprising a thrust bearing situated near the turbine. If the shaft carrying the turbine breaks, these arrangements lead to rubbing of the blades of the turbine rotor against the stationary blading of the stator. Although the blades may be destroyed, more substantial damage and the consequences thereof will be prevented.
It is an object of the invention to provide an improved solution to these problems, particularly for applications where use of previously known solutions is difficult or impossible. In particular, it is an object of the invention to provide a solution which reduces the extent or damage to the parts and prevents destruction of the blades, yet guarantees efficient braking of the turbine rotor and facilitates reconditioning operations after an accident, the implementation of the solution remaining simple and not overburdening the equipment, this being an important criterion, particularly for aeronautical applications.
According to the invention there is provided a gas turbine engine including a compressor and a turbine, said compressor and the turbine each having a rotor, a common shaft interconnecting said compressor and turbine rotors whereby the compressor is driven by said turbine, and an exhaust casing adjacent the downstream end of the turbine in the direction of flow of gases through the turbine, wherein the turbine rotor carries a conical ring at the downstream end thereof, and the exhaust casing carries on the upstream the thereof a structural member of generally conical shape disposed such that, in the event of breakage of the common shaft, the conical portions of the ring and structural member come into contact with each other in a manner which brakes the turbine.
Other features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, with reference to the attached drawings.